Hemodynamics and left ventricular function: a comparison between adult racing greyhounds and greyhounds completely untrained from birth

Trained racing greyhounds are known to have cardiomegaly, higher mean arterial pressure and cardiac indices and lower systemic arterial resistances at rest than mongrel dogs. In order to distinguish between those hemodynamic and left ventricular functional characteristics that are inborn in the greyhound as opposed to those which are acquired through training, we studied 9 adult (mean age 22.9±4.2 [S.D.] months) trained racing greyhounds within 8 days of the cessation of training and 9 adult greyhounds raised under sedentary conditions (mean age 21.7±1.4 months). Seven healthy adult mongrel dogs served as additional controls. Right and left heart catheterizations of chloraloseanesthetized animals included hemodynamic and left ventricular functional measurements before and after volume loading with 500 ml 6% dextran in normal saline. Heart weight/body weight ratios were the same in both trained and untrained greyhounds, favoring the concept that the cardiomegaly of greyhounds is genetic and not acquired. Trained greyhounds had significantly decreased systemic vascular resistance, increased cardiac index and stroke volume, and a tendency (non significant) toward elevated systemic arterial pressure in comparison to mongrels. Life-long untrained adult greyhounds had hemodynamic measurements that did not differ from mongrels; they also had significantly higher systemic vascular resistances and lower cardiac indices than trained greyhounds. Some hemodynamic characteristics of the trained adult greyhound dog are not present in completely untrained greyhounds and are the result of either training alone or training superimposed on genetic predisposition.